It is possible to overcome the EDD's initial ruling on appeal if you can prove that you were actually terminated through no fault of your own and not for misconduct.
Unfortunately, considering the "litany of issues" that indicated that you did not manage two accounts properly and the fact that you had previously been cited ("warned") by your manager, it will be difficult to obtain a reversal of the decision on appeal, but it is still definitely possible.
To do so, you will likely need proof of your good job performance, including any performance reviews that you may have, and any other documented instances where you were informed that you were doing a good job.
This would work to counteract the argument that you were terminated for misconduct, and that your employer is only actually alleging that you were terminated for misconduct to avoid having to pay you unemployment benefits.
You can read more about discharges for misconduct to prepare your argument in your letter and appeal hearing:http://www.edd.ca.gov/uibdg/Misconduct_MC_5.htm
As I mentioned previously, the odds are, unfortunatley, likely against you, but it is still definitely worthwhile to appeal, since it is quite possible that an administrative judge would see the situation differently than EDD did initially.
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